I used a quarter oz. to goose a Berliner I made, my first. It had not soured much at all after four months, despite having a one liter starter made from apple juice and acid malt, plus a slant of WL lacto. D. The sourness took off after adding the lactose (just poured the powder in), but I think it oxidized somehow, because it darkened from a pale straw color to a pale amber. Next time I'll take more care to minimize O2 exposure.